Environmental campaigners have attacked Asda and Sainsbury's for failing to reduce the number of plastic bags they use when delivering food to customers who buy online.

Despite sustained pressure from consumers and the green lobby, new research suggests that both supermarket chains often use more plastic bags in their home deliveries than most of their rivals, sometimes putting only two or three items in each bag. A survey by trade magazine The Grocer found that on one occasion Asda used 15 bags to pack just 32 items. When the same survey was conducted three months earlier it had used 14 plastic bags for 33 items. In the latest survey Sainsbury's used 11 bags for 33 items, having previously used only six carriers for that number of items in the test three months ago.

Other supermarkets emerged from the survey with much more environmentally friendly statistics. To deliver the same 33 items Tesco used just four bags while Waitrose used five suggesting that concern about waste management is being heeded by some supermarkets.

Pressure groups nevertheless reacted angrily to the findings. Peter Robinson, director of Waste Watch, an independent charity, said: "It is encouraging that some supermarkets are taking their obligations toward the environment seriously. But clearly others have a very long way to go."

He highlighted the particular difficulties associated with online shopping. "When customers are actually in a supermarket they have a much greater degree of control over the amount of plastic they take home with them," he said. "But with online shopping the consumer loses that control. All the evidence suggests that when consumers are given a choice they increasingly reject unnecessary packaging. Supermarkets need to take responsibility for giving them that choice even when it comes to buying online."

Vicki Hird, at Friends of the Earth, said the report proved that some supermarkets were "not doing nearly enough" to tackle environmental degradation. "It is ridiculous that only two or three items should be put into one bag. It's a totally unnecessary waste of resources," she said. "We need much more pressure from governments on supermarkets, including fiscal pressure. We need to create incentives for managing waste properly. Of course the consumer could do more, but it must start with government pressure on the big stores".

Campaign groups are emphasising the importance of re-using and returning bags. "Customers should be handing back excess baggage to delivery van drivers," said Mr Robinson. A spokeswoman for Asda appeared to endorse such action, saying: "Customers can give their plastic carrier bags back to the driver who will take them back to the store for re-cycling." Admitting that Asda has in the past given customers unnecessary baggage, she added: "Feedback from customers is that they like their bangers separate from their bleach. But in this case it does look like the number of carrier bags we used was excessive."

On average, British consumers use 290 plastic bags a year, close to one a day. The nine major supermarket chains distribute more than 17.5 billion bags a year.

Echoing the message from Asda about returning unwanted bags, a spokesman for Sainsbury's said: "We are always looking for new ways to divert plastic bags from landfill and many customers now use our service of giving back used bags to drivers, so they can be recycled."

(By Amol Rajan, The Independent, 04/09/2007)